1. Field of the Invention
This invention relates to a single-acting, gas-operated, reciprocating pump for use in pumping syrup in a post-mix beverage dispensing system, and more specifically to such a pump that is inexpensive, quiet, that has no priming problem, that has an inherent sold-out feature, and that has little tendency to stall.
2. Description of the Prior Art
There are presently two general types of syrup pumps on the market. At one end of the spectrum are the double-acting, gas-powered, diaphragm pumps, such as that shown in U.S. Pat. No. 4,436,493. These pumps work on demand and because they have a relatively long, slow stroke they prime very well. At the other end of the spectrum are fast cycling electric pumps. These pumps do not prime very well because they have relatively short, fast strokes. Electric pumps must be fitted with pressure switches before they can work on demand.
It is an object of the present invention to provide an inexpensive, gas-operated syrup pump.
It is another object of the present invention to provide an inexpensive, gas-operated syrup pump that has no priming problems.
It is a still further object of the present invention to provide a syrup pump that has an inherent sold-out feature.
It is another object of the present invention to provide a single-acting, gas-operated pump that is sized to cycle at a rate of from about 0.5 to 15 cycles per second, and to dispense from about 0.25 to 0.5 ounces of syrup per second.
It is still another object of the present invention to provide a single-acting, gas-operated reciprocating pump that includes a piston assembly stem that is mechanically coupled to the stem of the gas control valve by a snap-acting spring mechanism, and that includes a counteracting spring on the control valve stem.